1. Field of the Invention
The present invention relates to an interdental cleaning tool for insertion between adjacent teeth to effect cleaning of the interdental gap, and to a method for the manufacture thereof.
2. Description of the Related Art
An interdental cleaning tool for insertion between adjacent teeth to effect cleaning of the interdental gap is fabricated by arranging a plurality of cirrate members fabricated from synthetic resin along a deflected piece produced by deflection of a single strand of wire into a xe2x80x9cUxe2x80x9d shape in the longitudinal central portion of, grasping the deflected piece at a first end and a second end thereof and twisting the deflected piece so that the cirrate members become embedded therein, and then severing the ends of the cirrate members to produce uniform cirrate member length, the article so fabricated being attached via one end of the wire to a handle of predetermined length fabricated from synthetic resin.
Apropos, in the interdental cleaning tools available commercially, cirrate members fabricated from synthetic resin are embedded in wire, and as the wire on occasion flexes during use, and as the cirrate members are moreover embedded in this wire by means of twisting, there may occur deviation in the anchoring force of the cirrate members to the wire, namely, in the extraction force of the cirrate members. Further, where an interdental cleaning tool is constructed using wire, there is required a process wherein the wire is deflected into a xe2x80x9cUxe2x80x9d shape, the cirrate members are arranged along the deflected piece, and the deflected piece is twisted so that the cirrate members become embedded therein, and it is further necessary to attach the wire to a handle of predetermined length, resulting in the problem of complexity of process and high cost. Further, the use of exposed wire creates the problem of a lack of a soft sensation against the tissues of the oral cavity.
There has been proposed previously an interdental cleaning tool that does not employ wire, being fabricated in its entirety from synthetic resin; however, this has been proposed merely in conceptual terms, the particulars thereof having yet to be suggested, with such a product remaining to be commercially developed.
With the foregoing in view, it is an object of the present invention to provide a process for the manufacture of an interdental cleaning tool wherein a shaft member and projections composed of pinnulate members and/or cirrate members are integrally molded from synthetic resin, thereby affording a soft sensation against the tissues of the oral cavity and eliminating any deviation in extraction force of the pinnulate members and cirrate members.
The interdental cleaning tool pertaining to a first invention is an interdental cleaning tool having one or a plurality of projections on the peripheral face of a shaft member, wherein the projections are pinnulate members and/or cirrate members, the shaft member and projections being integrally molded from synthetic resin.
According to the first invention, projections and a shaft member for insertion into gaps between adjacent teeth are integrally molded from synthetic resin, affording a soft sensation against the tissues of the oral cavity during use. Further, as the synthetic resin projections are integrally molded with shaft member, variation in projection extraction force is eliminated. Moreover, as the projections and shaft member constitute an integrally molded structure, manufacture involves a fewer number of manufacturing steps than does a corresponding product using wire, thus affording reduced cost.
Where the projection is a pinnulate member, cleaning performance by an individual projection is enhanced and projections are rendered highly durable.
According to the interdental cleaning tool pertaining to a second invention, projections are molded using a mold provided with cavities for forming projections, situated on parting faces thereof that intersect the axis of the shaft member or on parting faces thereof that are codirectional with the axis.
According to the second invention, a structure is possible wherein a plurality of projections are arranged codirectional with the circumference and axis of the shaft member, affording enhanced cleaning performance. The use of a split mold facilitates intricate machining of mold cavities.
According to the interdental cleaning tool pertaining to a third invention, projection size, namely pinnulate member thickness or cirrate member diameter, is 0.2 mm or smaller.
According to the third invention, maximum thickness for a pinnulate member or diameter for a cirrate member participating in interdental cleaning is 0.2 mm or smaller, whereby the pinnulate member or cirrate member is rendered flexible so as to give a pleasant sensation during use. Where pinnulate member maximum thickness or cirrate member diameter exceeds 0.2 mm, pinnulate members or cirrate members will lack flexibility, resulting in an unpleasant sensation during use.
According to the interdental cleaning tool pertaining to a fourth invention, projection length is 0.5 mm or greater.
According to the fourth invention, projections are 0.5 mm or greater in length, affording adequately enhanced cleaning performance. Where projections is shorter than 0.5 mm, the excessively short length of the projections, which participate in interdental cleaning, results in diminished cleaning performance.
The interdental cleaning tool pertaining to a fifth invention is provided with a plurality of projections, with pinnulate member density centered about the shaft member being at least 3 per 360xc2x0 and cirrate member density in the axial direction of the shaft member being at least 8 per 1 mm of length.
According to the fifth invention, pinnulate member density centered about the shaft member is at least 3 per 360xc2x0 and cirrate member density in the axial direction of the shaft member is at least 8 per 1 mm, thereby affording sufficiently good cleaning performance. Where pinnulate member density is less than 3 per 360xc2x0 or cirrate member density is less than 8 per 1 mm, the resulting inadequate pinnulate member/cirrate member density will result in diminished cleaning performance.
According to the interdental cleaning tool pertaining to a sixth invention, a projection comprises a projection proper connecting to the shaft member and a branch member(s) integrally formed therewith and extending in a direction that intersects the axis of the projection proper.
According to the sixth invention, projections proper and branch members participate in interdental cleaning, increasing the number of points of contact with the tooth, thereby affording further enhanced cleaning performance.
According to the interdental cleaning tool pertaining to a seventh invention, the shaft member has a core element consisting of a material having a flexural modulus higher than the flexural modulus of the aforementioned synthetic resin, produced by insert molding or two-color molding. In the seventh invention, xe2x80x9ccore element consisting of a material having a flexural modulus higher than the flexural modulus of the aforementioned synthetic resinxe2x80x9d will naturally include metal materials, and will include synthetic resin materials as well. Insert molding refers to a process wherein the core element is vised in a mold and a synthetic resin material then flowed into the mold; two-color molding refers to a process wherein the core element is formed first, followed by molding of other portions, including projections.
According to the seventh invention, projections which participate in interdental cleaning are endowed with good flexibility, excessive flexion of the shaft member is prevented, and shaft member strength is increased.
According to the interdental cleaning tool pertaining to an eighth invention, the material for the core element of the shaft member is synthetic resin having a flexural modulus higher than the flexural modulus of the synthetic resin used for projections.
According to the eighth invention, projections which participate in interdental cleaning are endowed with good flexibility, excessive flexion of the shaft member is prevented, and shaft member strength is increased.
According to the interdental cleaning tool pertaining to an ninth invention, the material for the core element of the shaft member is metal.
According to the ninth invention, there is no a twisting process, as with interdental cleaning tools using wire, and thus the core element may be composed of a highly rigid material such as piano wire, precluding bending of the shaft member. That is, wire material that will be subjected to a twisting process must have appreciable elongation, which precludes the use of highly rigid wire materials; here, the fact that the core element is simply subjected to insert molding means that a highly rigid material can be used.
The use of highly rigid metal also allows the diameter of the inserted core element to be thinner. By using a shape memory alloy (e.g. , Nixe2x80x94Ti alloy, etc.) an interdental cleaning tool having become bent through use may be restored by immersing it in hot water.
According to the interdental cleaning tool pertaining to a tenth invention, the shaft member is molded from a synthetic resin having a flexural modulus higher than the flexural modulus of the synthetic resin used for the projections, and is molded integrally with the projections.
According to the tenth invention, the shaft member and projections can be integrally molded using within the mold one synthetic resin for the projections and another synthetic resin for the shaft member, thereby affording pliable projections as well as increased strength of the shaft member and affording a pleasant sensation during cleaning between the teeth.
According to the interdental cleaning tool pertaining to an eleventh invention, the shaft member and projections are injection molded from thermoplastic resin.
According to the eleventh invention, a finished interdental cleaning tool can be molded easily by melting thermoplastic resin at a suitable temperature and flowing the melt into a mold. The product will have softer contact against oral cavity tissues than will an interdental cleaning tool having synthetic resin cirrate elements embedded in wire, as in the conventional art example.
According to the interdental cleaning tool pertaining to a twelfth invention, the shaft member and the projections are injection molded from a thermoplastic elastomer.
According to the twelfth invention, the exceptional recovery of the thermoplastic elastomer prevents permanent bending of the shaft member, and the exceptional elasticity affords softer contact against oral cavity tissues.
According to the interdental cleaning tool pertaining to a thirteenth invention, the shaft member and projections are injection molded from a thermoplastic resin or thermoplastic elastomer having flexural modulus of 6000 kgf/cm2 or above and a melt flow index of 8 g/10 min or above.
According to the thirteenth invention, the shaft member and projections resist bending owing to a flexural modulus of 6000 kgf/cm2 or above and are rendered more highly durable. A melt flow index of 8 g/10 m in or above gives synthetic resin good flow when filling the mold, eliminating short shot in the cavities and giving a good molded shape. Where flexural modulus is below 6000 kgf/cm2, the shaft will not insert well between teeth owing to inadequate strength. Where melt flow index is below 8 g/10 min, synthetic resin will have poor flow into the mold, making it difficult to produce projections of the desired length. A higher melt flow index is desirable, with 15 g/10 min or above being preferred, and 25 g/10 min or above being especially preferred.
According to the manufacturing method pertaining to a fourteenth invention, an interdental cleaning tool is manufactured using an injection mold divided into two sections along the axis of the shaft member.
According to the fourteenth invention, an interdental cleaning tool whose shaft member is provided with a plurality of projections may be molded using a mold having a simple construction.
According to the manufacturing method pertaining to a fifteenth invention, an interdental cleaning tool is manufactured using an injection mold split into three or more sections along the axis of the shaft member.
According to the fifteenth invention, the number and density of projections of an interdental cleaning tool whose shaft member is provided with a plurality of projections may be increased.
According to the manufacturing method pertaining to a sixteenth invention, an interdental cleaning tool is manufactured using a mold having a parting section in a mold section for molding projections. In the sixteenth invention, xe2x80x9cparting sectionxe2x80x9d refers to both mating portions for opening the mold and mating portions of the split mold not used for opening the mold.
According to the sixteenth invention, as a mold section is filled with synthetic resin, gas present in the mold section can escape to the outside through gaps in the parting section, allowing the synthetic resin to migrate up to the end of the mold section without the need to provide a special gas vent opening, thereby giving projections of desired length.
According to the manufacturing method pertaining to a seventeenth invention, an interdental cleaning tool is manufactured using a split mold having cavities for molding projections situated on a parting face thereof that intersects the axis of the shaft member.
According to the seventeenth invention, intricate machining of a plurality of cavities on parting faces of a split mold may be accomplished readily, whereby it is a simple matter to create a split mold for providing a plurality of projections along the circumference of the shaft member so that manufacturing costs for the interdental cleaning tool may be reduced. Further, gas present in a cavity can be vented through a gap between the parting faces, allowing the synthetic resin to migrate up to the end of the cavity without the need to provide a special gas vent opening. Cavities may be deliberately placed under negative pressure for molding.
According to the manufacturing method pertaining to an eighteenth invention, the split mold has thickness of from 0.1 to 2 mm in a direction intersecting the parting faces thereof.
According to the eighteenth invention, spacing between projections in the direction of the axis of the shaft member is small, viz., 0.1 to 2 mm, so that it is a simple matter to increase the number and density of projections arranged over the entire lengthwise extension of the shaft member.
According to the manufacturing method pertaining to a nineteenth invention, an interdental cleaning tool is manufactured using a mold split into three or more sections along the axis of the shaft member, the parting faces thereof being provided with cavities for molding projections.
According to the nineteenth invention, it is a simple matter to form cavities for a plurality of projections on the parting faces of a mold split into three or more sections, whereby an interdental cleaning tool having a plurality of projections arranged codirectional with the axis and circumference of the shaft member can be manufactured at reduced cost.